TECHNICAL FIELD OF THE INVENTION
The invention relates to a method of metering charges for data transmission, and in particular, to data transmission on at least two terminals operated on a data transmission network where a data transmission path is set up between the terminals.
BACKGROUND OF THE INVENTION
In conventional telephone service, in which circuit-switched transmission networks are used, call control and allocation of network resources are controlled by exchanges, which in each case perform both control functions. As a result, the charge metering is comparatively simple to control.
Due to decoupling of call control and the allocation of network resources, the conventional control methods can only simulate with considerable expenditure. Therefore, a fundamentally different method is contemplated.
SUMMARY OF THE INVENTION
In one embodiment of the invention, there is a method of metering charges for data transmission which, in particular, permits a large number of charge metering modes and, in particular, makes the unjustified use of transmission resources more difficult. Furthermore, a terminal suitable for carrying out the method, an associated control unit, program and electronic credit are to be provided.
In another embodiment of the invention, two terminals operate on a data transmission network and store at least one electronic credit. The credit includes a statement on the amount of use of transmission units of the data transmission network. Data transmission units of the network are controlled by two control units, located for example at the ends of a data transmission path. The terminals transmit a credit for use of the data transmission path to the control unit located on the respective side of the data transmission path. Depending on the credit received, the control unit clears the transmission units of the data transmission network to use the data transmission path. If the credit is valid, clearance takes place. If, on the other hand, the credit is invalid, the transmission units cannot be used for the transmission path.
An electronic credit authorizes use of the transmission units to a limited extent. No additional measures for clearing the transmission units have to be taken because, after the use fixed by the credit, the network resources can automatically be used for other purposes, unless a new credit arrives or has already arrived with the first credit. The electronic credits can be transmitted with previously used transmission protocols. For example, the credits are sent in electronic mail, known as e-mails.
The method of the invention contemplates the problem of controlling access to the transmission units of the data transmission network from two different control units, problems which do not occur when there is central control. In the case of decentralized controllers, call control is with the terminals, while the data transmission network is left to allocate the necessary resources, for example a specific transmission capacity with a specific transmission quality. Charge metering has to be carried out for the network resources. In the case of decentralized controllers, it is assumed that both the A side and the B side of a call have to request network resources from the network, for example bandwidths at the respective network access. The method also contemplates the situation where the clearance of network resources of both terminals is directly instigated by only one terminal require complex protocols. To avoid having to use such protocols, electronic credits are used in the method according to the invention.
In another embodiment of the invention, one terminal sends another terminal at least one electronic credit and can indirectly control the use of network resources by the other terminal. The credit coming from one terminal is sent by the terminal receiving the credit to the control unit which is located on the same side of the transmission path as the terminal concerned. In this regard, call metering methods in which the call metering component can be fixed within broad limits can be defined between the two terminals before the data transmission.
If the calling A side is to pay for the entire call, in a way corresponding to conventional charge metering in a fixed network, i.e. also in particular for the resources reserved by the B side, the following problem arises when setting up the call. The A side, as the paying subscriber, has an interest in clearing the resources involved in a call when the call is terminated, in order to stop the charge metering as well. For the B side, on the other hand, there is no reason to do this, since the B side is not paying for the resources. The correct charge metering for the network resources would consequently no longer be ensured. Here it is likewise assumed that the resource can in each case be cleared only by the side requesting it. Similar considerations also apply if the B side is the paying side and the use of network resources by the A side is to be paid by the B side.
In a refinement, the terminal beginning the data transmission, i.e. the A side, therefore sends the credit or the credits. In this refinement, the classic metering method, in which the call is only paid for by the caller, is used. The same considerations also apply, however, to a data transmission of computer data outside a conversation. The problem mentioned above can be solved in by the use of credits, which permit the use of network resources to a restricted extent. In an alternative embodiment, the credit is sent by the terminal responding to a network-side request for data transmission, i.e. the terminal of the B side. Such charge metering is used when offering services which are free of charge for the caller.
Alternatively, the A side sends the B side every second credit which the B side uses. The credits required in the interim are obtained by the B side from somewhere other than from the terminal of the A side.
In another embodiment of the invention, the electronic credits are issued in conjunction with the data transmission path which is to be set up or has already been set up. Misuse of the credits is made even more difficult by this measure. In a refinement, the electronic credit includes statements which identify the data transmission path:
an identification of the terminal beginning the data transmission,
an identification of the other terminal,
an identification for the interface used in the data transmission of the terminal beginning the data transmission, for example a port number,
an identification for the interface used in the data transmission of the other terminal, and/or
an identification for a transmission protocol used in the data transmission.
The statements included in the electronic credit are checked by the control units. The credit can be used for the transmission path which is specified by the statements. The statements mentioned have the effect in particular of making it even more difficult for the credits to be used twice or more.
In another embodiment of the invention, a period of validity or a date of validity is fixed for the credits. For example, the credits include a date and/or a time of day, the value of which indicates a point in time at which the credit loses its validity. As a reference point for this time, Central European Time or a time fixed for use of the Internet may be chosen for example. The period of validity is fixed on the basis of a call metering unit. For example, the call metering time five minutes after the credit is issued is chosen. In the case of other credits, a period of validity of one minute or less than one minute is chosen, for example 30 seconds. In particular in the case of credits which both include the statements relating to the transmission path and are restricted in their period of validity, a high level of security in the use of the credits is achieved.
In another embodiment of the invention, the statements included in the credits are protected with the aid of a cryptographic method. The control units check the genuineness of the credits with the aid of the cryptographic methods. Such cryptographic methods are included for example in the standard X.509 laid down by the ITU-T (International Telecommunication Union—Telecommunication Sector). Consequently, certification chains are used when issuing the credits. With the aid of the cryptographic methods it can be ensured that the credit is actually issued by an authorized agency. Additionally, it can be checked in a whether the credit has been changed. One frequently used method is the DES algorithm (Data Encryption Standard) or the RAS algorithm (Rivest, Shamir, Adleman). It can be ensured by an electronic signature that misuse of the credits is restricted.
The data transmission network is, for example, a packet-switched network operating according to the Internet Protocol, for example the Internet. However, the method is also used in other data transmission networks, for example in ATM networks (Asynchronous Transfer Mode) The method according to the invention or its various embodiments can also be used, however, in classic circuit-switched networks.
For setting up and clearing down the data transmission path on a higher protocol layer, preferably the protocol SIP (Session Initiation Protocol) is used, laid down by the IETF (Internet Engineering Task Force) in the RFC2543 (Request for Comment). Alternatively, a protocol of the H.323 protocol family is used for connection control. These protocols have been laid down by the ITU-T. In particular, the protocols H.225 and H.245 belong to this protocol family. However, other suitable protocols are also used.
For allocating the network resources, the protocol RSVP (Resource Reservation Protocol) is used, laid down by the IETF in RFC2205. Alternatively, a different protocol or method of allocating network resources may also be used, however. For instance, the protocol DiffServ (Differentiated Service) is used, see RFC244.
The method according to the invention and the various embodiments are used in particular for the transmission of voice data in real time. Real time means that, after they have been generated, the voice data have to be transmitted within less than 250 ms, for example, from one terminal to the other terminal. In voice services, it is particularly important for the acceptance of these services that different methods of charging are used. What is more, specifically in the case of the transmission of voice data, attention must be paid to the prevention of misuse.
The invention also relates to a terminal and a control unit which are constructed in such a way that the method according to the invention or one of its embodiments is performed during their operation. Furthermore, the invention relates to a program which is required for performing the method according to the invention and the various embodiments. The technical effects mentioned above apply to the terminal, the control unit and the program.
The invention also relates to an electronic credit which is suitable for use in the method according to the invention or in one of its developments. The credit includes statements which fix the amount of use of transmission units of the data transmission network. If appropriate, the credit includes statements concerning the transmission path and statements concerning validity. The use of cryptographic signature and/or encryption methods allows the possibility of misuse of the credit to be restricted. For example, the credit is formed by digital data of a data record which are structured in accordance with predetermined data fields.